This invention relates generally to a precompression pump sprayer, and more particularly to a pump chamber priming arrangement for such sprayer.
As known, the manually actuated precompression pump sprayer, otherwise referred to as a pressure build-up pump sprayer, has a reciprocable discharge valve member which opens the discharge at a threshold pump pressure reached during pumping as pump chamber pressure exceeds the force of a return spring. The threshold pressure may not be reached to open the discharge while the pump chamber contains air, which is compressible. Thus, for the precompression pump sprayer to function satisfactorily, the pump chamber must first be primed, i.e., the unwanted air in the chamber must be evacuated and replaced by liquid product to be dispensed.
One approach taken in priming the pump chamber of a precompression sprayer is disclosed in U.S. Pat. No. 4,051,983 wherein a longitudinally extending rib or groove is formed on the inner wall of the bore of the pump housing in which the reciprocable discharge valve operates. A nose of the discharge valve, in the form of a popper valve, is normally seated against a discharge valve seat formed in the discharge passage of a hollow piston stem, under the action of an opposing spring force provided by the piston return spring. At the threshold pressure, the popper valve is forced away from its valve seat to open the discharge, in the known manner.
The popper valve has a seal in sliding sealing engagement with the bore in which the valve reciprocates. As the air in the unprimed pump chamber is compressible, the piston and poppet valve are lowered together upon depressing the plunger. At or near the end of the plunger downstroke, the seal between the poppet seal and the wall of the bore in which the poppet operates is interrupted when the poppet seal is juxtaposed to the rib or groove. The air in the pump chamber, which has now been compressed during the piston downstroke, is evacuated from the pump chamber directly into the container via the dip tube extending into the liquid product in the container. The compressed air flows down the tube by capillary action until product partially fills the pump chamber on each ensuing upstroke which draws liquid product into the pump chamber. As liquid product partially fills the pump chamber, it prevents the remaining volume of air in the pump chamber from being evacuated past the popper seal and into the container. This remaining volume of air must now be purged from the chamber to avoid issuance through the discharge orifice causing an undesirable sputtering and uneven spray.
Another approach taken in priming the pump chamber of a precompression pump sprayer is exemplified by U.S. Pat. No. 5,064,105, wherein one or more small protuberances is formed on the wall of the pump chamber for deforming the piston seal at or near of the end of the piston downstroke permitting unwanted air from the pump chamber to be evacuated into the container via a side port formed in the pump housing.
A still further arrangement provided for priming the pump chamber is disclosed in U.S. Pat. No. 4,923,094 in which the popper valve has a radially outwardly extending base which, at the end of the plunger downstroke, engages a projection on an inner wall of the closure forming a priming step for causing a poppet valve seal to shift away from its confronting wall to open a path for evacuating air from the pump chamber into the container via a container vent.